(1) Field of the Invention
The present invention pertains to an air flow baffle used in an dynamoelectric device that has a novel shape that increases air cooling of the device. More specifically, the present invention pertains to an air flow baffle that is positioned in the casing shell of a dynamoelectric device between the stator and a cooling fan of the device, where the air flow baffle directs a flow of cooling air across the dynamoelectric device while reducing flow separations and pressure losses in the air flow and thereby more efficiently cools the dynamoelectric device.
(2) Description of Related Art
Many dynamoelectric devices such as appliance motors for dishwashers, clothes washers and dryers and whirlpool baths utilize fans mounted on their rotor shafts to provide for air cooling of the stators and rotors of the motors during their operation. Typically, the fan is mounted at one axial end of the device and is shaped to pull or push air through the housing or casing shell of the device across the stator and rotor, thereby cooling the device.
The typical dynamoelectric device, for example a generator or motor, includes a generally cylindrical housing or casing shell with a pair of end shields or end bells mounted to the axially opposite ends of the casing shell. The stator of the device is secured to an interior surface of the shell and the rotor of the device is mounted for rotation on the housing end shields. The cooling fan of the device mounted on the rotor typically has an outer diameter that is dimensioned to be received in the interior of the casing shell or the interior of one of the end shields. Mounting the fan on an end of the rotor shaft with the fan contained in the device prevents objects from contacting the fan blades during operation of the device.
The electrical windings of the stator of a dynamoelectric device typically generate the most heat during operation of the device. To provide efficient cooling of the dynamoelectric device, it is desirable that the air flow drawn through the device or pushed through the device by the fan be directed in close proximity across the stator, and that the rate or velocity of the air flow be maximized. For example, in an electric motor it is desirable to direct a flow of cooling air across the stator windings of the motor, in particular across the winding end turns, and to increase the velocity of the air flow in order to provide the most efficient convective cooling of the stator windings.
In prior art dynamoelectric devices such as electric motors, air flow baffles have been employed to direct a flow of cooling air across the stator of the motor. In one such electric motor design that employs a fan to draw cooling air through the motor, the baffle is typically a flat disk that is positioned between the stator and the fan that draws the cooling air through the motor. Air flow baffles used in electric motors are typically constructed from either stamped steel or molded plastic. The baffle disk has an outer perimeter edge that is secured to the interior of the motor casing shell. The outer perimeter of the baffle is typically provided with a cylindrical rim that engages with the casing shell interior surface. The baffle also has a circular inner edge that surrounds a center hole of the baffle through which the rotor shaft passes. The center opening is dimensioned larger than the rotor shaft of the motor to provide ample clearance for the flow of air from the stator and rotor on one side of the baffle to the fan on the opposite side of the baffle.
On operation of the electric motor, the rotating rotor shaft also rotates the fan. The fan rotation draws a flow of air through the baffle center hole from the portion of the casing shell containing the stator and rotor on one side of the baffle, to the opposite side of the baffle occupied by the rotating fan. The cooling air is drawn through the center of the motor across the rotor and the center of the stator, and is also drawn across the outer perimeter of the stator between the stator and the interior surface of the casing shell. The flow of air drawn across the outer perimeter of the stator is redirected radially inwardly by the baffle toward the baffle center hole. This radially inward flow of air cools the wiring end turns of the stator winding. After passing across the stator wiring end turns, the radially inwardly directed flow of air is then drawn through the baffle center hole to the side of the baffle occupied by the rotating fan. The air is then ejected from the motor casing and/or end shield by the rotation of the fan.
Prior art baffle designs have been found to be disadvantaged in that they employ right angle corners where the outer perimeter rim of the baffle joins the flat baffle disk as well as right angle corners at the inner edge of the baffle surrounding the baffle center hole. The right angle corners have a tendency to cause flow separation of the cooling air drawn through the casing shell, causing an undesirable pressure loss and resulting in lower air flow rates and velocity. By decreasing the flow velocity, the cooling efficiency of the baffle is decreased.